The present invention relates to optical fiber connector apparatus, and, more particularly, to connector apparatus for accurately aligning a pair of optical fibers in abutting end-to-end relationship.
It is often necessary to connect the ends of two optical fibers to one another so that light can be transmitted from one fiber to the other. When connecting the two fibers, it is important that the loss of signal as a result of the transfer of the light from one fiber to the other be as low as possible, i.e., that there be a minimal insertion loss. When optical fibers are joined end-to-end, insertion loss can result from center-to-center mismatch, angular misalignment of the fiber axes, fiber to fiber separation, the finish of the ends of the fibers and other factors.
For optical fibers having a diameter of about 125 microns, misregistration of the centers of the two fibers by only 0.5 microns can result in a loss of as much as 1 db. For reasonably low insertion losses, therefore, the centers of the fiber end faces must be registered within at least about 12.5 microns, and preferably less.
A variety of apparatus for connecting a pair of optical fibers in end-to-end relationship with respect to one another are known in the art.
In one known type of connector, optical fibers are inserted into opposite ends of a cylindrical tube until they come into contact with one another. The fibers are then simply clamped or otherwise locked into position within the tube. In some connectors of this type, the tube is provided with a bore of V-shape or other configuration in order to achieve a more accurate alignment between the two fibers.
Connectors of this type are not fully satisfactory for several reasons. For one thing, any dirt within the cylinder bore can easily get between the two fibers and cause interference in the passage of light between the fibers or physically damage the ends of the fibers. The clamping step can also damage or distort the fragile fibers.
Frequently, the end of an optical fiber is terminated in a ferrule or termination member so that the fiber end can be more easily managed; and a number of connectors have also been developed to align ferrule-terminated fibers. For example, one type of connector comprises an elastomeric sleeve which expands radially inward to maintain the ferrule-terminated fibers in alignment. Such connectors, however, have been found to be less likely to provide an accurate and repeatable alignment than rigid connectors.
Connectors including longitudinally split spring members into which the ferrules are pushed for aligning the ferrules with one another are also known. These connectors usually require one or more additional components between the ferrules and the connector housing which increases both the cost and the complexity of the connector.